Multiple-disc type filters generally include a housing in which the filter body within the housing is in the form of a stack of like, centrally-apertured, filter discs having grooved side faces defining filtering channels between the adjacent discs in the stack. In some applications of such filters, the outer face of the stack of filter discs constitutes the upstream side of the filter, in which case the fluid being filtered passes from the outer face to the inner face of the stack. In other applications of such filters, the inner face of the stack constitutes the upstream side of the filter, in which case the fluid being filtered passes from the inner to the outer face through the filter stack.
A multiple-disk type filter into which there is incorporated extensible support apparatus is disclosed in the applicant's U.S. Pat. No. 4,642,182 issued Feb. 10, 1987. The filter includes a stack of filter disks in a housing and an extensible support for the stack of filter disks disposed internally thereof, the extensible support including first and second base elements and a multiplicity of rod members joining the first and second base elements in sliding relationship, a first plurality of the rod members being fixedly attached to the first base element and being arranged for slidable supporting engagement with the second base element and a second plurality of the rod members being fixedly attached to the second base element and being arranged for slidable supporting engagement with the first base element.
In view of the internal disposition of the extensible support relative to the stack of filter disks, however, the support does not facilitate the introduction of a cleaning nozzle, or other similar cleaning apparatus, internally of the stack without first disassembling it. It is particularly important to be able to introduce cleaning apparatus internally of the stack, especially where the inner face of the stack is also the downstream face.